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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
** Thread Private Data
**
** There is an aribitrary limit on the number of keys that will be allocated
** by the runtime. It's largish, so it is intended to be a sanity check, not
** an impediment.
**
** There is a counter, initialized to zero and incremented every time a
** client asks for a new key, that holds the high water mark for keys. All
** threads logically have the same high water mark and are permitted to
** ask for TPD up to that key value.
**
** The vector to hold the TPD are allocated when PR_SetThreadPrivate() is
** called. The size of the vector will be some value greater than or equal
** to the current high water mark. Each thread has its own TPD length and
** vector.
**
** Threads that get private data for keys they have not set (or perhaps
** don't even exist for that thread) get a NULL return. If the key is
** beyond the high water mark, an error will be returned.
*/
/*
** As of this time, BeOS has its own TPD implementation. Integrating
** this standard one is a TODO for anyone with a bit of spare time on
** their hand. For now, we just #ifdef out this whole file and use
** the routines in pr/src/btthreads/
*/
#include "primpl.h"
#include <string.h>
#if defined(WIN95)
/*
** Some local variables report warnings on Win95 because the code paths
** using them are conditioned on HAVE_CUSTOME_USER_THREADS.
** The pragma suppresses the warning.
**
*/
#pragma warning(disable : 4101)
#endif
#define _PR_TPD_LIMIT 128 /* arbitary limit on the TPD slots */
static PRInt32 _pr_tpd_length = 0; /* current length of destructor vector */
static PRInt32 _pr_tpd_highwater = 0; /* next TPD key to be assigned */
static PRThreadPrivateDTOR *_pr_tpd_destructors = NULL;
/* the destructors are associated with
the keys, therefore asserting that
the TPD key depicts the data's 'type' */
/*
** Initialize the thread private data manipulation
*/
void _PR_InitTPD(void)
{
_pr_tpd_destructors = (PRThreadPrivateDTOR*)
PR_CALLOC(_PR_TPD_LIMIT * sizeof(PRThreadPrivateDTOR*));
PR_ASSERT(NULL != _pr_tpd_destructors);
_pr_tpd_length = _PR_TPD_LIMIT;
}
/*
** Clean up the thread private data manipulation
*/
void _PR_CleanupTPD(void)
{
} /* _PR_CleanupTPD */
/*
** This routine returns a new index for per-thread-private data table.
** The index is visible to all threads within a process. This index can
** be used with the PR_SetThreadPrivate() and PR_GetThreadPrivate() routines
** to save and retrieve data associated with the index for a thread.
**
** The index independently maintains specific values for each binding thread.
** A thread can only get access to its own thread-specific-data.
**
** Upon a new index return the value associated with the index for all threads
** is NULL, and upon thread creation the value associated with all indices for
** that thread is NULL.
**
** "dtor" is the destructor function to invoke when the private
** data is set or destroyed
**
** Returns PR_FAILURE if the total number of indices will exceed the maximun
** allowed.
*/
PR_IMPLEMENT(PRStatus) PR_NewThreadPrivateIndex(
PRUintn *newIndex, PRThreadPrivateDTOR dtor)
{
PRStatus rv;
PRInt32 index;
if (!_pr_initialized) {
_PR_ImplicitInitialization();
}
PR_ASSERT(NULL != newIndex);
PR_ASSERT(NULL != _pr_tpd_destructors);
index = PR_ATOMIC_INCREMENT(&_pr_tpd_highwater) - 1; /* allocate index */
if (_PR_TPD_LIMIT <= index)
{
PR_SetError(PR_TPD_RANGE_ERROR, 0);
rv = PR_FAILURE; /* that's just wrong */
}
else
{
_pr_tpd_destructors[index] = dtor; /* record destructor @index */
*newIndex = (PRUintn)index; /* copy into client's location */
rv = PR_SUCCESS; /* that's okay */
}
return rv;
}
/*
** Define some per-thread-private data.
** "index" is an index into the per-thread private data table
** "priv" is the per-thread-private data
**
** If the per-thread private data table has a previously registered
** destructor function and a non-NULL per-thread-private data value,
** the destructor function is invoked.
**
** This can return PR_FAILURE if index is invalid (ie., beyond the limit
** on the TPD slots) or memory is insufficient to allocate an expanded
** vector.
*/
PR_IMPLEMENT(PRStatus) PR_SetThreadPrivate(PRUintn index, void *priv)
{
PRThread *self = PR_GetCurrentThread();
/*
** To improve performance, we don't check if the index has been
** allocated.
*/
if (index >= _PR_TPD_LIMIT)
{
PR_SetError(PR_TPD_RANGE_ERROR, 0);
return PR_FAILURE;
}
PR_ASSERT(((NULL == self->privateData) && (0 == self->tpdLength))
|| ((NULL != self->privateData) && (0 != self->tpdLength)));
/*
** If this thread does not have a sufficient vector for the index
** being set, go ahead and extend this vector now.
*/
if ((NULL == self->privateData) || (self->tpdLength <= index))
{
void *extension = PR_CALLOC(_pr_tpd_length * sizeof(void*));
if (NULL == extension)
{
PR_SetError(PR_OUT_OF_MEMORY_ERROR, 0);
return PR_FAILURE;
}
if (self->privateData) {
(void)memcpy(
extension, self->privateData,
self->tpdLength * sizeof(void*));
PR_DELETE(self->privateData);
}
self->tpdLength = _pr_tpd_length;
self->privateData = (void**)extension;
}
/*
** There wasn't much chance of having to call the destructor
** unless the slot already existed.
*/
else if (self->privateData[index] && _pr_tpd_destructors[index])
{
void *data = self->privateData[index];
self->privateData[index] = NULL;
(*_pr_tpd_destructors[index])(data);
}
PR_ASSERT(index < self->tpdLength);
self->privateData[index] = priv;
return PR_SUCCESS;
}
/*
** Recover the per-thread-private data for the current thread. "index" is
** the index into the per-thread private data table.
**
** The returned value may be NULL which is indistinguishable from an error
** condition.
**
*/
PR_IMPLEMENT(void*) PR_GetThreadPrivate(PRUintn index)
{
PRThread *self = PR_GetCurrentThread();
void *tpd = ((NULL == self->privateData) || (index >= self->tpdLength)) ?
NULL : self->privateData[index];
return tpd;
}
/*
** Destroy the thread's private data, if any exists. This is called at
** thread termination time only. There should be no threading issues
** since this is being called by the thread itself.
*/
void _PR_DestroyThreadPrivate(PRThread* self)
{
#define _PR_TPD_DESTRUCTOR_ITERATIONS 4
if (NULL != self->privateData) /* we have some */
{
PRBool clean;
PRUint32 index;
PRInt32 passes = _PR_TPD_DESTRUCTOR_ITERATIONS;
PR_ASSERT(0 != self->tpdLength);
do
{
clean = PR_TRUE;
for (index = 0; index < self->tpdLength; ++index)
{
void *priv = self->privateData[index]; /* extract */
if (NULL != priv) /* we have data at this index */
{
if (NULL != _pr_tpd_destructors[index])
{
self->privateData[index] = NULL; /* precondition */
(*_pr_tpd_destructors[index])(priv); /* destroy */
clean = PR_FALSE; /* unknown side effects */
}
}
}
} while ((--passes > 0) && !clean); /* limit # of passes */
/*
** We give up after a fixed number of passes. Any non-NULL
** thread-private data value with a registered destructor
** function is not destroyed.
*/
memset(self->privateData, 0, self->tpdLength * sizeof(void*));
}
} /* _PR_DestroyThreadPrivate */
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